The replacement Tripler came in but the result is the same as the old part. All low voltages are good until the tripler's HV input connection is soldered in, at which point, the same fuse F 558 blows. I thought it may be the CRT itself but disconnecting the EHT lead still does not resolve the issue. Removing the CRT base socket has no effect either. Since the only time the fuse blows is when pin 10 of the HV transformer is connected to the tripler's HV input even with the EHT plug disconnected, my guess is that the EHT transformer is drawing a heavy current on the primary when this connection is made.
Unfortunately, I have no way to confirm this as a replacement EHT transformer is not available. So, sadly, I may have to give up on this. If any members have any ideas, I will be glad to hear them.
Thanks.